First of all, you should undergo one blood test for beta HCG level and TVS scan to confirm or exclude product of conception.
Other reasons are hormonal imbalance, vaginal infection
with co-existence of stress/ anxiety, thyroid disorder
, ovarian cyst
, irregular diet habit etc.
Treatment depends on underlying etiology. Consult with your gynecologist at the earliest for other relevant investigation if any.
Avoid stress, take healthy diet with iron supplements
, control body wt, maintain genital hygiene properly and take proper sleep.
Be well & take care.